hash_set::equal_range

Returns a pair of iterators respectively to the first element in a hash set with a key that is equal to a specified key and to the first element in the hash set with a key that is greater than the key.

pair <const_iterator, const_iterator> equal_range ( 
   const Key& _Key 
) const; 
pair <iterator, iterator> equal_range ( 
   const Key& _Key 
);

Parameters

• _Key
  The argument key to be compared with the sort key of an element from the hash_set being searched.

Return Value

A pair of iterators where the first is the lower_bound of the key and the second is the upper_bound of the key.

To access the first iterator of a pair pr returned by the member function, use pr.first, and to dereference the lower bound iterator, use *(pr.first). To access the second iterator of a pair pr returned by the member function, use pr.second, and to dereference the upper bound iterator, use *(pr.second).

Remarks

In Visual C++ .NET 2003, members of the <hash_map> and <hash_set> header files are no longer in the std namespace, but rather have been moved into the stdext namespace. See The stdext Namespace for more information.

Example

// hash_set_equal_range.cpp
// compile with: /EHsc
#include <hash_set>
#include <iostream>

int main( )
{
   using namespace std; 
   using namespace stdext;
   typedef hash_set<int> IntHSet;
   IntHSet hs1;
   hash_set <int> :: const_iterator hs1_RcIter;
   
   hs1.insert( 10 );
   hs1.insert( 20 );
   hs1.insert( 30 );

   pair <IntHSet::const_iterator, IntHSet::const_iterator> p1, p2;
   p1 = hs1.equal_range( 20 );

   cout << "The upper bound of the element with "
        << "a key of 20 in the hash_set hs1 is: "
        << *(p1.second) << "." << endl;

   cout << "The lower bound of the element with "
        << "a key of 20 in the hash_set hs1 is: "
        << *(p1.first) << "." << endl;

   // Compare the upper_bound called directly 
   hs1_RcIter = hs1.upper_bound( 20 );
   cout << "A direct call of upper_bound( 20 ) gives "
        << *hs1_RcIter << "," << endl
        << "matching the 2nd element of the pair"
        << " returned by equal_range( 20 )." << endl;

   p2 = hs1.equal_range( 40 );

   // If no match is found for the key,
   // both elements of the pair return end( )
   if ( ( p2.first == hs1.end( ) ) && ( p2.second == hs1.end( ) ) )
      cout << "The hash_set hs1 doesn't have an element "
           << "with a key greater than or equal to 40." << endl;
   else
      cout << "The element of hash_set hs1 with a key >= 40 is: "
           << *(p1.first) << "." << endl;
}

The upper bound of the element with a key of 20 in the hash_set hs1 is: 30.
The lower bound of the element with a key of 20 in the hash_set hs1 is: 20.
A direct call of upper_bound( 20 ) gives 30,
matching the 2nd element of the pair returned by equal_range( 20 ).
The hash_set hs1 doesn't have an element with a key greater than or equal to 40.

Requirements

Header: <hash_set>

Namespace: stdext

See Also

Reference

hash_set Class

Standard Template Library